Chemistry Solutions Essay

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E1. Write an equation to show the equilibrium that exists between NaI(s) and Na+(aq) and I–(aq). AE1. NaI(s) ( Na+(aq) + I–(aq) E2. a Sketch a graph of the change in the radioactivity of the solution over time. b On the same axes, sketch a graph of the change in the radioactivity of the solid over time. AE2. a, b [pic] Q1. a By referring to the equilibrium: H2O(l) ( H2O(g) explain what is meant by the ‘dynamic nature’ of chemical equilibrium and why wet clothes in a closed laundry bag do not dry. b When the bag in part a is opened the clothes begin to dry. Is this due to an equilibrium process? Explain your answer. A1. a Chemical equilibrium is ‘dynamic’ because both forward and reverse reactions occur at the same rate. An equilibrium develops between water vapour and water when wet clothes are in a sealed bag, with water evaporating as rapidly as water vapour condenses, so the clothes remain wet. b When the bag is opened, water vapour escapes and the rate of evaporation exceeds the rate of condensation. The system is not in equilibrium and the clothes dry. Q2. Write an expression for the equilibrium constant for the following equations. a 2NH3(g) ( N2(g) + 3H2(g) b 4NH3(g) + 3O2(g) ( 2N2(g) + 6H2O(g) c Cu2+(aq) + 4NH3(aq) ( Cu(NH3)42+(aq) d Ni2+(aq) + 6NH3(aq) ( Ni(NH3)62+(aq) A2. a K = [pic] b K = [pic] c K = [pic] d K = [pic] Q3. At 255°C the equilibrium constant is 100 M2 for the reaction: 2NH3(g) ( N2(g) + 3H2(g) a Write an expression for the equilibrium constant for the equation: N2(g) + 3H2(g) ( 2NH3(g) b Calculate the equilibrium constant for the equation in part a. c Write an expression for the equilibrium constant for the equation: NH3(g) ( [pic]N2(g) + [pic]H2(g) d Calculate the equilibrium constant for the equation in part c. e Use your answers to parts a to d to

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